This change uses the read_avail and '.info_mask_shared_by_type_available'modifier to set the available scale.Essentially, nothing changes to the driver's ABI.

The main idea for this patch is to remove the AD7793 driver fromcheckpatch's radar. There have been about ~3 attempts to fix/break the'in_voltage-voltage_scale_available' attribute, because checkpatch assumedit to be an arithmetic operation and people were trying to change that.